Beer, red wine, and high unit price energy drink are generally contained in glass containers. The high gas barrier characteristic of the glass blocks oxygen outside the bottle from entering the bottle and carbon dioxide inside the bottle from leakage, in order to maintain the quality, flavor or freshness of the contents in the bottle. A glass bottle is heavy and fragile, and costs high in manufacturing, loading and transferring processes. In recent years, plastic containers come to the market, and replace the glass bottle gradually. However, plastic containers suffer from a poor gas barrier characteristic. For example, PET has a gas barrier characteristic as low as 10−1 g/bottle·day. Plastic bottles with such a low gas barrier characteristic can neither ensure the quality of carbonated beverage contained therein, nor be mass-produced. Therefore, plastic containers with a film coated therein come to the market.
Currently, inner and outer electrodes are used to coat a film. The inner electrode, which is made of a conductive material, is inserted into the body of a plastic container. As plasma stimulates and dissociates a diamond like carbon (DLC) precursor, a nano-scaled DLC film will be formed on an inner wall of the body of the plastic container. Such a technique has a drawback. Since the inner electrode is in direct contact with the coating environment, when the coating process is performed for a period of time, containments will be accumulated on the inner electrode. The containments may fall and remain in the bottle, and contaminate the contents contained in the bottle.
The inner electrodes have to be cleaned from time to time, in order to prevent the coated film from falling and remaining in the bottle. Such an action increases the cost.
Therefore, how to overcome the problems of existing prior art that spend a great amount of time and money to clean the inner electrodes is becoming one of the most urgent issues in the art.